In The Mysteries of the Prayer and Its Important Elements, book four of the 40 books of the Revival of the Religious Sciences, Abū Hāmid al-Ghazālī explains the inner and outer meanings of the prayer, a central practice for Muslims. He explains the acts involved in the outward elements of the prayer and outlines which of these acts are obligatory and which are sunna. He then discusses the inward requisites of the prayer--the practices of the heart-- and presents practical remedies for a distracted heart. He also discusses the annual prayers and the prayers and supplications related to events such as eclipses, the prayer for rain, guidance, and need. This readable yet comprehensive work covers an array of issues from the essential outward aspects of how to pray, to the inward aspects of the state of the heart during the prayer and how to humble oneself completely. As a practical, yet profound book, it is essential reading for Muslims who seek a deeper comprehension of prayer, and for all those interested in understanding the meaning and place of prayer in Islam.